The Ethereal Border existed adjacent to the Material Realm; according to the Cosmic Wheel model, it was a transitive Realm, and connected it to all other Inner Realms. When travelers crossed into the Ethereal, they and all their possessions were converted to their Ethereal equivalents: metal became ethereal metal, flesh became ethereal flesh, and so on. This allowed movement in any direction through the solid matter of the adjacent plane, and there was a sense of "up" and "down", though no real gravity existed.
Creatures on the Ethereal could see into the Prime Material, but could not affect the energies of the plane. However, certain creatures dwelled primarily on the Border and could shift between it and the Material Plane virtually at will. Examples of these included Ghosts and Phase Spiders.